Can you confirm if you have Windows Live Movie Maker 2011 or if you have upgraded to Movie Maker 2012? Go to the File menu and look under About Movie Maker to know for sure.
Have you installed anything on your system recently that might have affected Movie Maker? Say an updated driver or a system update? One thing you could try is a System Restore back to before the problem started happening.
Alternatively, if you have a screenshot of the issue, it might help us diagnose the problem further. Perhaps you could put a photo up on imgur.com or a similar site and post a link to it.